Some
infections are mild & barely noticeable, but others are severe &
life-threatening, & some are resistant to treatment. Infection easily can
be transmitted in a variety of ways. These include skin contact,
bodily fluids, contact with feces, airborne particles, & touching an object
that an infected person has also touched. How an infection spreads & its
effect on the human body depend on the type of agent.

The
immune system is very effective barrier against the infectious
agents, but colonies of pathogens may grow too large for the immune system to
fight. At this stage, infections become harmful.

They
are classified by the different type of organism causing the infection.

Infections
can range from the mild inflammation in one person to an epidemic.

Symptoms

As
well as the site of the infection, the symptoms of an infection depend on the
organism responsible. Viruses target specific cells, such as those in the upper
or genitals respiratory tract. The rabies virus, for example, targets
the nervous system (Fastly). Some viruses target skin cells, causing warts.
Others target a wider range of cells in body, leading to various symptoms.
A flu virus can cause a runny nose, muscle aches, & an upset
stomach.

A
person with a bacterial infection will often experience redness & heat,
swelling, fever, pain at the site of infection, & swollen lymph glands. A
bacterial infection is less likely to affect a wide area of human body than a
viral one. Common symptoms of prion diseases include brain damage, memory loss,
& cognitive difficulties.

Prevention

There
is no single way to prevent the all infectious diseases, but the following tips
can reduce the risk of transmission:

Wash your hands often,
especially before & after preparing food & after using the bathroom.